Virtualization of computer resources generally involves abstracting computer hardware, which essentially isolates operating systems and applications from underlying hardware. Hardware is therefore shared among multiple operating systems and applications wherein each operating system and its corresponding applications are isolated in corresponding virtual machines (VM) and wherein each VM is a complete execution environment. As a result, hardware can be more efficiently utilized.
A VM executing on a virtualized computer system will typically be limited to hardware resources (such as memory space, CPU cycles, network bandwidth, and so on) provided by that virtualized computer system, i.e., VMs executing on a first virtualized computer system typically share the hardware resources of the first virtualized computer system, and VMs executing on a second virtualized computer system typically share the hardware resources of the second virtualized computer system. As such, the performance of a VM will depend on the hardware resources of the virtualized computer system on which the VM is executing, as well as demands of any other VMs executing on the same virtualized computer system.
One aspect of virtualization is an ability to live migrate workload transparently from one host computer of a virtualized computer system to another, where live migration is sometimes referred to as VMotion. With VMotion, workloads can be dynamically balanced among host computers. In addition, VMotion enables hardware maintenance to be performed without service interruption by migrating a workload off a host computer that needs to be shut down.
Existing VMotion solutions work well in a data center environment where all virtualization software runs on top of a single physical network. However, this imposes a limitation for users that need to perform VMotion across networks, such as migrating VMs to a remote network at a different site to enable sharing of resources across diverse geographical locations or implementing seamless disaster avoidance solutions.